Despite the importance of the hydrogen ion in a wide range of biological, chemical, and physical processes, its molecular structure in solution remains lively debated. Progress has been primarily hampered by the extreme diffuse nature of the vibrational signatures of hydrated protons in bulk solution. Using the inherently surface-specific vibrational sum frequency spectroscopy technique, we show that at selected negatively charged interfaces, a resolved spectral feature directly linked to the H3O+ core in an Eigen-like species can be readily identified in a biologically compatible pH range. Centered at ~2540 cm-1, the band is seen to shift to ~1875 cm-1 when forming D3O+ upon isotopic substitution. The results offer the possibility of tracking and understanding from a molecular perspective the behavior of hydrated protons at charged interfaces.

中文翻译：

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在带负电的界面上识别本征状水合质子。

尽管氢离子在广泛的生物，化学和物理过程中具有重要意义，但其在溶液中的分子结构仍然存在激烈的争论。本体溶液中水合质子的振动信号的极端扩散性主要阻碍了这一进展。使用固有的特定于表面的振动和频率光谱技术，我们显示出在选定的带负电的界面上，可以容易地在生物相容的pH范围内识别出与本征状物种中的H3O +核直接相关的分辨光谱特征。在同位素取代后形成D3O +时，以〜2540 cm-1为中心，可见该带移至〜1875 cm-1。结果提供了从分子角度跟踪和理解带电界面上水合质子行为的可能性。